The invention relates to the field of telecommunications. More particularly, the invention relates to the quality of communication made available to mobile terminals attached to stations, referred to as “server” stations, that transmit and/or receive in the radiofrequency range (e.g. cellular networks).
Mobile terminals, such as smartphones and personal computers (PC) are nowadays capable of activating and using several logical interfaces associated with one or more physical interfaces. Such terminals are said to be “multi-interface” (MIF) terminals.
A plurality of IP addresses can then be allocated to such MIF terminals in order to connect to different types of network such as a wireless local area network (WLAN), or a cellular network.
In this respect, it should be observed that the invention is compatible with all types of WLAN networks, e.g. WiFi networks in compliance with the 802.11 standard of the Institute of Electrical and Electronics Engineers (IEEE). The invention is also compatible with all types of cellular networks, e.g. those that make use of GMS/GPRS technology as defined in version 97, and subsequent versions of the GSM standard, or that make use of universal mobile telecommunications system (UMTS) technology as defined in particular in the 23.002, 23.003, and 29.060 standards of the third-generation partnership project (3GPP), or that make use of long-term evolution (LTE) technology, or indeed of “femto 3G” technology as defined in 3GPP document TR 25.820 V8.2.0 (2008 September).
For a mobile terminal having access to at least one radiocommunications network having a certain number of server stations, the procedure for allocating resources usually takes place as follows:
a) the terminal scans the various pilot signals that it can receive, and for each respective pilot signal it measures the respective loss over the propagation path (“path loss”);
b) when the terminal seeks to initiate communication, it sends a request for attachment to the server station providing the most powerful received pilot signal, indicating in this request said path loss together with the data rate desired for the communication;
c) this request for attachment reaches a management center (internal or external) in charge of managing the server station;
d) as a function of said path loss and of the load on the server station, the management center decides whether or not to authorize the request attachment; and
e) if accepted, the management center decides as a function of the load on the server station whether to grant the resources requested in order to obtain the data rate desired by the terminal, in full or in part only.
Once attached to the network, i.e. once connected to a server station, the terminal is conventionally suitable for measuring a signal over interference plus noise ratio (SNR) relating to the signal received from the server station, and to transmit this SNR value to the server station. The server station may then, by way of example on the basis of the SNR value, determine the best modulation and coding scheme for the communication. As explained in detail below, the greater the SNR, the better the quality of the communication.
An MIF terminal that has the means and the rights for accessing a plurality of networks ought thus to seek attachment to the network that will give it the best SNR, once it has become attached. The problem that arises under such conditions is knowing how the terminal can discover the respective SNR values of the respective networks to which it has access before any attachment, or the SNR that it would have on a second network while it is already attached to a first network.
In a first known solution, the operator of the network uses simulators that rely on theoretical models for describing the reality of the terrain, e.g. electromagnetic wave propagation models or models of the data exchange traffic in the network.
The main limitation of such simulations is associated with the accuracy of the models.
In a second known solution, radio conditions in a network may advantageously be measured within the network by terminals belonging to users of the network. Provision is thus made for the mobile terminals belonging to a terrestrial mobile radio network such as a GSM network, or a UMTS network, or an enhanced data rates for GSM evolution (EDGE) network, or indeed a network of the WIMAX type, to take measurements in the network under consideration either periodically or following predefined events. Thus, the proposal entitled “MDT measurement model” (meeting No. 68bis of the RAN W2G standardization group of the 3rd generation partnership project (3GPP), Valencia, Spain, Jan. 18 to 22, 2010) discloses a radio measurement system in which a management entity of a UMTS terrestrial radio access network (UTRAN) broadcasts a message requesting the mobile terminals of users to take a measurement of a specified nature in a specific geographical zone (that system is known as the minimization of drive tests (MDT) method). The terminals of the network receiving the request decide whether or not to take the requested measurement, in particular as a function of whether or not they are situated in the measurement zone, which they can determine by means of a positioning system such as a global positioning system (GPS) device with which they are equipped; each terminal that has taken the measurement can store the results of the measurement and transmit them to said UTRAN network at a predetermined instant. The network can then discover the SNR that might characterize a communication with a first terminal, on the basis of the SNR characterizing, at the same instant, a communication with a second terminal that is geographically very close to the first terminal.
The drawback of that second solution is that these need not be any such second terminal.
In a third known solution, the operator of a network uses a database in which to accumulate the results of SNR measurements at various locations and at various times (day of the year, time of day). If the database has sufficient data, the operator can find therein the SNR as measured at the same location as the terminal in question, on the previous day at the same time, or on the same day and at the same time last year, and so on.
The drawback of that third solution is that it assumes that reception conditions are reproduced periodically at a location of the network. Unfortunately, such an assumption is not realistic, in particular because of weekly and seasonal fluctuations, and also because of rapid variations in the architecture of the network in order to satisfy the rapidly increasing demand for data rate from users.